But other critics, like Francois Balloux of University College London, raised concerns over the way the study was conducted even though they are sceptical the drugs themselves would work as a treatment for COVID-19.
"I think both sides - one side who is saying "this is a risky drug" and the other side that says "this works" - neither is correct", said Boulware.
The study, using data provided by healthcare data analytics firm Surgisphere, was not a traditional clinical trial that would have compared hydroxychloroquine to a placebo or other medicine.
The Lancet has now published an expression of concern around the Surgisphere study. "It does not prevent infection", he said of the drug.
This study was in younger relatively healthy people, but the results "would make me very discouraged about trying to use this in older people" who are most vulnerable to serious illness from the coronavirus, Bach said.
Side effects, however, were more common with hydroxychloroquine group than those on the placebo - 40.1 percent versus 16.8 percent - no serious ones were reported though.
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A much-anticipated study, co-authored by Canadian researchers, has found that hydroxychloroquine - a drug much-touted by U.S. President Donald Trump - was not effective in fighting COVID-19 in a trial this spring.
Trump repeatedly has pushed hydroxychloroquine, an anti-malarial drug that also is used to treat lupus and rheumatoid arthritis, as a preventative or cure for COVID-19 and said he took the drug for more than a week despite cautions against doing so from the Food and Drug Administration.
"The Executive Group will communicate with the principal investigators in the trial about resuming the hydroxychloroquine arm, " he said.
Trump and Brazilian President Jair Bolsonaro discussed a joint research effort on using hydroxychloroquine as both a prophylaxis and treatment for the coronavirus, the White House said on Tuesday.
The scientists then monitored the outcome in the patients, and noted if there was either laboratory-confirmed COVID-19 diagnosis, or if they developed illness compatible with the disease within 14 days.
The statement has come after more than 100 scientists from across the globe wrote an open letter to the editor of The Lancet, Richard Horton, questioning the validity of the study which assessed the safety and effectiveness of hydroxychloroquine (HCQ) in COVID-19 treatment.
All considered, the study's results are "more provocative than definitive, suggesting that the potential prevention benefits of hydroxychloroquine remain to be determined", Cohen said in the editorial.
"Our data is pretty clear that for post-exposure, this does not work", University of Minnesota infectious disease physician and lead researcher, Dr. David Boulware, told Reuters.
Study limitations noted by the authors are the lack of availability of diagnostic testing for COVID-19 in the USA, which the healthcare workers were unable to access, meaning a prior symptomatic case definition was used, or a US clinical case definition of probable COVID-19.